Jasper, DA, Hoffman, P, Banning, NC, Wiseman, GS, Stanbury, KE, Annison, SJ & Henderson, GR 2019, 'Current practice and innovation in decommissioning, rehabilitation and monitoring on Barrow Island: applications for mine closure', in AB Fourie & M Tibbett (eds), Proceedings of the 13th International Conference on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 63-74, https://doi.org/10.36487/ACG_rep/1915_06_Jasper
Decommissioning and rehabilitation of a land-based oilfield has many similar challenges to those faced in mine closure. In this paper we describe current practices for decommissioning, rehabilitation, and vegetation monitoring that is applied on Barrow Island, off the west-northwest coast of Western Australia. Barrow Island hosts both oil and gas production facilities and is an internationally significant A Class nature reserve. The island is particularly important for the presence of a diverse fauna, many of which have been lost, or are poorly-represented, on the Australian mainland.
More than 50 years of oil production, and more recently construction of the Gorgon liquefied natural gas facility, has required clearing of vegetation and earthworks for infrastructure, such as well pads, roads, pumping stations, gravel pits and pipeline corridors. Current decommissioning activities for the oilfield are conducted with a ‘clean as you go’ strategy, focused on the removal of redundant equipment and plant, which in turn opens opportunities for remediation and rehabilitation.
Accurate and cost-effective monitoring of vegetation establishment is an important part of rehabilitation and closure on Barrow Island, as it is for mine closure. Innovative technologies are changing the way environmental monitoring is conducted around the world. In Australia, with an extensive resource sector operating in relatively remote, arid environments there is opportunity to improve the accuracy and scale of environmental monitoring, while reducing health and safety risks, through technologies such as remote sensing.
Combining high-resolution imagery with object-based image analysis (OBIA) allows accurate delineation of vegetation types. This includes the potential to identify key species, over an entire study area, and allows greater insights on rehabilitation performance than standard transect or quadrat-based monitoring of representative areas. The data obtained can remove the potential for on-ground sampling bias, is scientifically repeatable and defensible to regulatory agencies. We applied the OBIA approach to the detection of grasses of the genus Triodia (‘spinifex’), which is endemic to Australia and dominate the hummock grasslands that cover around 18% of the continent. Many of Australia’s largest mineral resource extraction and oil and gas operations coincide with hummock grassland ecosystems. Therefore, understanding disturbance impacts and restoration outcomes of Triodia is critical to successful mine closure in these arid ecosystems.
The OBIA approach has a wide range of applications in addition to rehabilitation monitoring, such as vegetation condition monitoring or impact assessment, detection of invasive plant species or those of conservation interest and identification of fauna habitats or other features of interest in vast landscapes. Importantly it has potential to reduce time in the field, thus lowering health and safety risks in our remote and hostile arid environments. We present examples of use of this approach for vegetation impact assessment in natural communities and vegetation monitoring as part of site rehabilitation and closure.
Keywords: oilfield decommissioning, rehabilitation, remote sensing, object-based image analysis, Triodia, Barrow Island
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